Convective Cloud Research Current Projects: 1. CSIP 2. COPS 3. ICEPIC 4. RICO 5. APPRAISE 6. VOCALS (AG) 7. In-cloud temperature probe Possible Future.

Convective Cloud Research

Current Projects:

1. CSIP2. COPS3. ICEPIC4. RICO5. APPRAISE 6. VOCALS (AG)7. In-cloud temperature probe

Possible Future Projects:

Response to themes -- storms; network of sensors...

Constrain -- microphysics in UM (and WRF and MESO-NH?)Aerosol-Clouds (Amazon) -- Major international effortAerosol-Clouds: ICE-T and New Mexico -- Ice in convective clouds and influence of aerosols

Projects involve many people in ICAS from tea maker (me) to Head of ICAS andDirector of NCAS. Everyone important. ICAS is an excellent group.

Research on initiation of convection:

1. Convecitve Storm Initiation Project (CSIP): Southern England, summers of 2004 and 20052. Convective Orograpically-induced Precipitation Study (COPS): Black Forest, Germany, summer of 2007.

Flash Floods caused by intense rainfall associated with a thunderstorm

In the US, more people die yearly in floods (127 on average) than bylightning (73), tornadoes (65), or hurricanes (16)

In the UK: “Country in chaos after flash floods and storms”; a familiar headline now -- return time to severe events decreasing

While there had been:

Considerable research in the US; most recently IHOP_2002

Extensive research in UK: Modelling of case studies; Observational case studies using MO network instruments and satellite

There had been no previous UK experiment on convective initiation with which to compare Met Office model predictions

CSIP was a large international experiment centred on Chilbolton

18 IOPs in 2005; 4 IOPs in 2004

Met Office Model usually performed well, but someshortcomings in precise location and timings

Lids important; triggering often involves phenomena that actindividually or in concert to overcome lid

Variety of processes: no “generic triggering mechanism”.

CSIP

Map of CSIP

Thanks to Cyril Morcrette

COPS

Major international experiment in Black Forest mountains during summer of 2007.

Questions:

What is the role of upper tropospheric features for convective-scale QPFin moderate orographic terrain?

Does location and timing of CI depend on structure ofhumidity field in boundary layer?

Does precipitation intensity depend on aerosols?

What are pathways for heat, mass, water vapour and aerosolsassociated with thermally-driven flows to enterclouds?

Map of COPS

COPS and CSIP major objective: Determine location and timing of the initiation and development of convective storms.

Lids important.

Ways of overcoming Lids:

Convergence lines created by orography, land/sea contrasts, surface moisture gradients, differential heating

Heating; impact of clouds

In complex terrain: e.g. up-valley flow, elevated heat island;

Gravity waves and cold pools (secondary convection)

Mesoscale convergence lines and dry intrusions

Combination of processes

Frontal zone with low $\theta_w$ air overrunning a tongue of high$\theta_w$ air

Lid produced by descending dry intrusion

Lid relatively weak over surface warm pool -- strongest descent had occurred further upstream and the air was beginning to ascend again

Lid raised due to SW-NE convergence line mostly formed by land-sea roughness differences

Particular cloud initiated near Dartmoor and had sufficient buoyancy as a result ofcombination of high $\theta_w$ air and solar heating through gap in lineof clouds (Lean et al.\ 2008)

Convergence line + Up-valley flow

COPS 15 July

Another COPS objective: understand influence of aerosols on convective precipitation

- link to MMOCCAA and future expts

Venting of aerosols out of valleys into clouds Role of tranformation of aerosols by previous clouds Saharan dust outbreaks

Venting of water vapour and aerosolsfrom Murg Valley

Strong updraft over Murg associated with increase in humidity and concentrationof aerosols

ICEPIC: Study of the initiation and development of ice and precipitation in cumulus clouds.

1. First ice -- do the numbers match up with concentration of ice nuclei?

Don't know. Didn't manage this. Only way to do this in individual Cumulus clouds is to study clouds that are anchored to a feature - New Mexico(2012). Or statistically, as in RICO - ICE-T (2012?). Also see APPRAISE for mixed-phase layer clouds.

2. There are many more ice particles than ice nuclei -- why?

We showed quantitatively that the Hallett-Mossop process of secondary ice production can explain the observed rate of production of ice. MAC3 modelresults confirm that the HM process is important. However, MAC3 also shows thatsupercooled raindrops are important and we didn't observe these.

3. Explain quantitatively with models the production of precipitation -- that means getting the riming rate correct having explained 2.

The rain rate produced by MAC3 was comparable with the observed rate. BUT, the concentration of aerosols was critical.

ICEPIC (cont)

4. The UM has errors in the quantity of precipitation.

The interaction of the parametrized autoconversion and ice nucleation process can lead to an excessively rapid glaciation and vertical development of the simulated clouds. For example, in simulations of New Mexico clouds, autoconversion first occurred at and above the freezing level and the raindrops were then rapidly frozen by accreting primary ice crystals formed by the parametrized primary nucleation. These frozen raindrops then grew further by riming and, because this occurs with the temperature range of -3 to -8 C, acted as efficient centres of secondary ice nucleation via the Hallett-Mossop process. Similar for ICEPIC clouds.

Critical to get autoconversion right - see results from RICO. Alsofreezing -- see APPRAISE and future NM, ICE-T and CONSTRAIN?

RICO Study of the processes responsible for the formation of warm rain in shallow maritime cumulus clouds. (Rain In Cumulus over the Ocean)

Result: quantitatively explain the formation of rain in shallow maritim cumulus by collision and coalescence with MAC3 model using the observed aerosol size distribution. First time; 50-year old problem.

Observations

MAC3 Model

APPRAISE: Aerosol Properties, Processes And InfluenceS on the Earth's climate

determine the nucleating ability of specific ice nuclei and the initiation and development of ice in mixed phase clouds.• determine how aerosol particles control the cloud microphysics, preciptiation and dynamics in mixed phase clouds.• determine the type and phase partitioning of absorbing material above below and within clouds and the role of this material in ice nucleation.• reduce the uncertainty in the contribution of indirect radiative forcing by better understanding of the role of aerosols in the microphysics of mixed phase cloud.

Few flights last winter; most of the flying is in January and February 2009 over Chilbolton

Aerosol Interactions in Mixed Phase Clouds

Core position: Zhiqiang Cui -- bin microphysics in LEM. Almost complete. Important

C-130

BAe-146 Do-228

Multi-platform sampling along the 20°S cross section will deliver:

1. a synthesised data set for testing of climate model representations of the SEP boundary layer.

2. A series of important case studies

The VOCALS-UK Consortium will deliver new insights into the influence of marine stratocumulus clouds on global and regional climate and provide much needed improvements in our ability to quantify the processes that influence stratocumulus clouds and man’s influences on them.

Alan Gadian

VOCALS:VOCALS

Bridging the scales between climate and cloud processes

VOCALS will act to bridge the gap between climate models and key cloud processes by:

1) Diagnosing and testing important aspects of Climate model performance in Sc cloud regions – nested model resolution is key to this

2) Developing new process knowledge and parameterising it in a way that is effective for climate models

It will provide process studies with a climate backdrop to the VOCALS experiment – an important context

Courtesy Hugh Coe

In-Cloud temperature probe

Joint UFAM/FAAM/NCAR/Met Office project to produce a temperature probethat works in cloud.

Ophir radiometric probe is primary candidate: see Wei, Blyth and Raymond(1998; JAS)

Early stages for UK project; possible PhD student